Monohydrate of cis-lithium-cyano-4-[3-(cyclopentyloxy)-4-methoxyphenyl]cyclohexanecarboxylate

ABSTRACT

This invention provides a means for preparing a monohydrate of the lithium salt of cis 4-cyano-4-[3-(cyclopentyloxy)-4-methoxyphenyl]cyclohexanecarboxylate which is a novel composition of matter.

This application claims the benefit of provisional application No.60/178,129 filed Jan. 26, 2000.

AREA OF THE INVENTION

This invention relates to the preparation of a monohydrate of thelithium salt of cis4-cyano-4-[3-(cyclopentyloxy)-4-methoxyphenyl]cyclohexanecarboxylate,and the hydrate per se.

BACKGOUND OF THE INVENTION

Cyclic nucleotide phosphodiesterases (PDEs) represent a family ofenzymes that hydrolyze the ubiquitous intracellular second messengers,adenosine 3′,5′-monophosphate (cAMP) and guanosine 3′,5′-monophosphate(cGMP) to their corresponding inactive 5′-monophosphate metabolites. Atleast ten distinct classes of PDE isozymes are believed to exist, eachpossessing unique physical and kinetic characteristics and eachrepresenting a product of a different gene family. These aredistinguished using Arabic numerals 1-10.

A new approach toward improving the side effect profile of PDEinhibitors is to design a new generation of compounds that inhibit onlya single PDE isozyme, i.e., the PDE isozyme that predominates in thetissue of cell of interest. The predominate cAMP PDE isozyme in immuneand inflammatory cells is PDE4. It is also a major regulator of cAMPcontent in airway smooth muscle. Thus, selective inhibition of PdE4elevates cAMP content in immune and inflammatory cells, as well as inairway smooth muscle. This leads to anti-inflammatory effects as well asbronchodilation. One or both of these therapeutic actions are useful intreating a variety of diseases, including, but not limited to asthma andCOPD. PDE4 inhibitors, particularly PDE4-specific inhibitors are usefulalso in treating other diseases in the area of inflammation, (e.g.,asthma, chronic obstructive pulmonary disease, inflammatory boweldisease, rheumatoid arthritis), affects related to tumor necrosis factorand to cognition impairment (e.g., multi-infarct dementia, cognitivedysfunction, or stroke). This invention relates to a compound that isbetter tolerated than previous PDE4 inhibitors, namelycis-4-cyano-4-[3-(cyclopentyloxy)-4-metboxyphenyl]cyclohexane-1-carboxylicacid. More specifically this invention provides the hydrate of thelithium salt of this acid.

DESCRIPTION OF THE FIGURES

FIG. 1 is an ultraviolet spectrum for the Li monohydrate salt

FIG. 2 is an infrared spectrum of the Li monohydrate salt.

FIG. 3 is a tracing of a MS output for Formula (I) monohydrate

FIG. 4. is a flowchart of the MS ionization products for Formula (I)monohydrate.

SUMMARY OF THE INVENTION

This invention relates to cis-lithium4-cyano-4-[3-(cyclopentyloxy)-4-methoxyphenyl]cyclohexanecarboxylatemonohydrate which has the structure represented by Formula (I):

and a process for preparing it, as described below.

Specific Exemplification

A process for preparingcis-4-cyano-4-[3-(cyclopentyloxy)-4-methoxyphenyl]cyclohexane-1-carboxylicacid is described in several publications. See for example U.S. Pat. No.5,552,438 issued Sep. 3, 1996 and pending PCT application numberPCT/US98/02749 published on Aug. 13, 1998 as WO 98/34584 or PCTapplication US98/21-61 published Apr. 22, 1999 as WO 99/18793. Thesepublications, and others, teach how to make the Li salt of said acid.But those processes do not result in the preparation of a hydrate of theLi salt, including a monohydrate.

EXAMPLE 1

A lot of anhydrous lithium salt of the acid was prepared by the processdetailed in the afore-mentioned PCT applications WO 98/34584 and WO99/18793. The lot was crystallized from 80 mL of acetonitrile and 4 mLof water and rinsed with 9.5 mL of acetonitrile and 0.5 mL of water. Thefilter cake was then crystallized from acetonitrile and 4 mL of waterand rinsed with 9.50 mL of acetonitrile and 0.5 mL of water. Thematerial was dried in a vacuum oven (50° C., 20 inches) for 48 hours toprovide the monohydrate.

Appearance: white powder.

Ultraviolet Spectroscopy

The ultraviolet absorption spectrum of the monohydrate was measuredusing a Perkin-Elmer Lambda 7 spectrophotometer, for a solution of0.0076 mg/mL in methanol. The spectrum is dominated by the aromaticchromophore and conforms to other compounds in the series as shown inTable 1 and FIG. 1.

TABLE 1 Ultraviolet Absorption Bands Wavelength (nm) ε Assignment 20638,400 ¹B (aromatic) 231  9,600 ¹L_(a) 280  3,500 ¹L_(b)

Infrared Spectroscopy

The infrared absorption spectrum of the monohydrate Li salt was obtainedas a potassium bromide pellet using a Nicolet Magna 760 FT-IRspectrometer. The spectrum was measured with a resolution of 4 cm⁻¹. Thespectrum had band assignments shown in Table 2. The infrared spectrum isshown in FIG. 2.

TABLE 2 Infrared Band Assignments for lot KW-27173-68C0 Wavenumber(cm⁻¹) Assignment 3573 O—H stretch (water) 3319, 3208 O—H stretch (waterof hydration) 3100-3000 ═C—H stretches 3000-2800 —C—H stretches 2230nitrile stretch 1647 C═O stretch (acid) 1566 C═O stretch (carboxylate)and C═C stretches 1517, 1505 C═C stretches 1425 C—H deformation and C═Cstretches 1258, 1167, 1142 C—O stretches 811, 777, 734 aromatic C—Hdeformations

EXAMPLE 2 Karl Fischer Titration

Water was determined by Karl Fischer titration. A Mettler DL18instrument was used to carry out the determination. Reagents wereobtained from Cresent Chemical Co., Hauppauge, N.Y., USA and carried thetradename Hydranal (standard: sodium tartraqte-2-hydrate; titrant; andsolvent). Water content was found to be 5.14% w/w, which agreed with thetheoretical value for one molecule of water (4.91% w/w).

EXAMPLE 3 Thermogravimetric Analysis

The TG analysis of the lot prepared in Example 1 was conducted usingstandard procedures. A total weight loss of 4.96% was observed atapproximately 137° C. This weight loss is consistent with that of amonohydrate.

EXAMPLE 4 NMR Spectroscopy

The ¹H and ¹³C NMR spectra of the lithium salt monohydrate were measuredat 400.13 MHz and 100.63 MHz, respectively, using a Bruker InstrumentsAMX 400 spectrometer maintained at 25° C. The sample was prepared bydissolving 20.1 mg in 0.8 mL of DMSO-d₆ (99.96 atom % D, ISOTEC), andthe spectra were referenced to tetramethylsilane as a secondary solventreference. The proton and ¹³C GASPE (¹³C multiplicity editing via aGAted Spin Echo sequence) NMR spectra are shown in FIGS. 3 and 4, andthe ¹H and ¹³C data are consistent with the structure of a lithium saltmonohydrate of Formula (I).

Homonuclear two-dimensional information used for structural assignmentsinclude COSY (COrrelation SpectroscopY) data which were used to identifythe members of each proton spin system and NOESY (Nuclear OverhauserEffect SpectroscopY) data which indicated through-space nOeinteractions. The nOe data helped to establish the spatial relationshipbetween the individual spin systems and to define the stereochemicalrelationship between the 1- and 4-substituents. Heteronucleartwo-dimensional information used for structural assignments include HMQC(Heteronuclear Multiple Quantum Coherence) data that allowed forassignment of the protonated ¹³C signals via one bond correlations andHMBC (Heteronuclear Multiple Bond Coherence) data that allowed forassignment of quaternary ¹³C signals via multiple bond correlations. TheHMBC data also served to verify all of the previous ¹H and ¹³Cassignments. The chemical shift assignments for the monohydrate salt inDMSO-d₆ is summarized in Table 3.

TABLE 3 ¹³C Chemical ¹H Chemical ¹³C Shift, δ Shift, δ ¹H MultiplicityPosition (multiplicity) (integration) (J = Hz) 5 178.9 (s) 4′ 149.2 (s)3′ 147.0 (s) 1′ 133.7 (s) CN 123.1 (s) 6′ 117.5 (d) 6.99 (1H) dd (J =2.3, 9.2 Hz) 2′ 112.7 (d) 7.00 (1H) d (J = 2.3 Hz) 5′ 112.2 (d) 6.93(1H) d (J = 9.2 Hz) 1″  79.6 (d) 4.81 (1H) m CH₃O  55.6 (q) 3.72 (3H) s1  44.5 (d) 1.96 (1H) m 4  43.0 (s) 3  36.5 (2C, t) 2.06 (2H) m 1.76(2H) m 2″  32.2 (2C, t) 1.87 (2H) m 1.69 (2H) m 2  27.5 (2C, t) 2.01(2H) m 1.63 (2H) m 3″  23.6 (2C, t) 1.69 (2H) m 1.56 (2H) m

EXAMPLE 5 Desorption Chemical Ionization Mass Spectrometry

The desorption chemical ionization mass spectrum (DCI/MS) of the lithiumsalt monohydrate was obtained using a Nermag R30-10 triple quadrupolemass spectrometer. A 1:1 methanol:methylene chloride solution of themonohydrate was prepared at a concentration of 0.1 mg/mL. The sample wasintroduced into the mass spectrometer using a DCI probe. The probe washeated at a rate of 20° C./s. The reagent gas was ammonia. The massspectrum was scanned from 60 to 860 Da at a rate of 1.0 scans/s. Themass spectrum was acquired using a Mass Evolution EZScan data system andprocessed using the HP MS ChemStation software (FIG. 3).

The following molecular ion adducts were observed: [M+H]⁺ at m/z 344 and[M+NH₄]⁺ at m/z 361. Plausible ionic structures for the observedfragments that are consistent with the structure of Formula (I)monohydrate are given in FIG. 4.

What is claimed is:
 1. A compound which is the monohydrate of thelithium salt of cis4-cyano-4-[3-(cyclopentyloxy)-4-methoxyphenyl]cyclohexanecarboxylate. 2.A pharmaceutical preparation consisting of the monohydrate of thelithium salt of cis4-cyano-4-[3-(cyclopentyloxy)-4-methoxyphenyl]cyclohexanecarboxylate anda pharmaceutically acceptable expicient.
 3. A method for preparing themonohydrate of the lithium salt of cis4-cyano-4-[3-(cyclopentyloxy)-4-methoxyphenyl]cyclohexanecarboxylate,which method comprises treating an aliquot of anydrous lithium salt withacetonitrile and water.